Your Questions Answered

Design Engineering and Robert Bosch address some of the pressing issues of the day

Q: Our company has bought a company specialising in ESD manufacture. It is an area I am unfamiliar with, but I have to oversee the scoping of a new clean room installation. Can you provide me with guidance on the standards for clean rooms and some of the associated terminology?

A: Steve Yardley, product manager for Workstations and Handling Technologies at Bosch Automation Technology answers. (steveyardley@uk.bosch.com)

Clean room suitability is measured in accordance with the classification of the well-known US Federal Standard 209E, and the soon to be introduced internationally harmonised ISO 14644-1. The table contains the most important acceptable standards in the UK and for the new ISO 14644-1, scheduled to replace the UK standard in the not too distant future.

When planning your product facilities always bear these standards in mind. Bear in mind, too, that some suppliers now code their components according to the sterility level at which they can be used.

To answer the second part of your question, I have tried to bring together a basic glossary of terms. It is by no means complete, but should be of some use to you when beginning your discussions on the most appropriate designs for your new clean room installation:

* Air change frequency – Frequency of air change of the entire room volume per hour.

* Air sterility level – Level of particulate sterility as indicated by the maximum authorised number of particles

* Enclosure – Enclosures to create a local clean room can have their own filter-fan-unit or use the air supply in the clean room ceiling.

* Falling flow unit – Clean room installation, which blows a filtered mildly turbulent repressive current down vertically. The aim is to prevent airborne particulates rising above workbench level.

* Grey room – Portion of the clean room where the back-air of the clean room installation flows through. In high quality clean room installations even the service areas surrounding pure working areas are also described as grey rooms. They possess a better quality of air than the atmospheric surroundings, while still being burdened with particles coming from the clean room.

* HEPA filter – The High Efficiency Particulate Air Filter Unit is a filter with a shedding of at least 99.97%. That is to say it removes 99.97% of all particulates from the air.

* Modular clean room – Clean room installations whose high quality clean surfaces can be made larger, smaller or moved with little effort.

* SMIF technology – Technology in conjunction with the Standard Mechanical Interface used in semi-conducting for the automatic opening and closing of standardised transport containers (SMIF-containers). When using SMIF-containers production devices are equipped with local clean rooms.

* Virgin air – Filtered, prepared air, which streams from the end filter of a clean room installation and has not yet taken on any of the pollutants present in the clean room or been diverted.